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JeGX's DevBlog - Dynamic branching and NVIDIA Forceware Drivers
Dynamic branching and NVIDIA Forceware Drivers 
Tuesday, May 22, 2007, 12:56 PM - NVIDIA
Several weeks ago, I posted on Beyond3D a thread on my dynamic branching benchmark. I wondered why dynamic branching performances on Geforce 7 were worse than ones on Geforce 6 or 8. I believe I've got the answer: Forceware drivers.

Here are some new results where ratio = Branching_ON / Branching_OFF :

7600GS - Fw 84.21 - Branching OFF: 496 o3Marks - Branching ON: 773 o3Marks - Ratio = 1.5
7600GS - Fw 91.31 - Branching OFF: 509 o3Marks - Branching ON: 850 o3Marks - Ratio = 1.6
7600GS - Fw 91.36 - Branching OFF: 508 o3Marks - Branching ON: 850 o3Marks - Ratio = 1.6
7600GS - Fw 91.37 - Branching OFF: 509 o3Marks - Branching ON: 850 o3Marks - Ratio = 1.6

7600GS - Fw 91.45 - Branching OFF: 509 o3Marks - Branching ON: 472 o3Marks - Ratio = 0.9
7600GS - Fw 91.47 - Branching OFF: 509 o3Marks - Branching ON: 472 o3Marks - Ratio = 0.9
7600GS - Fw 93.71 - Branching OFF: 508 o3Marks - Branching ON: 474 o3Marks - Ratio = 0.9
7600GS - Fw 97.92 - Branching OFF: 505 o3Marks - Branching ON: 478 o3Marks - Ratio = 0.9
7600GS - Fw 100.95 - Branching OFF: 508 o3Marks - Branching ON: 480 o3Marks - Ratio = 0.9

my conclusion is: dynamic branching in OpenGL works fine (read the performance are better than without dynamic branching: ratio > 1) for forceware <= 91.37. For the drivers >= 91.45, the ratio drops under 1. Dynamic branching works as expected for gf6 and gf8 but not for gf7 since forceware 91.45. So the bug explanation is a plausible answer (and it's easily understandable: in this news , we learnt that a forceware driver is made of around 20 millions of lines of code - a paradise for a small bug!!!). I've also done the test with the simple soft shadows demo provided with the NV SDK 9.5. The results are the same.

I've just done the bench with a 7950gx2 and the latest forceware 160.02 and dynamic branching is still buggy...

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